Data Transfer Apparatus, Data Transfer Device, and Data Transfer Method in a Data Transfer Device

1. A data transfer apparatus comprising: a first port and a second port that communicate data; a memory unit that stores the data; a securing unit that secures, when a first time period starting from transmission of data up to reception of a response to transmitted data at the first port is longer than a second time period starting from transmission of data up to reception of a response to transmitted data at the second port, a first memory space that is used in data transfer in the first port so as for the first memory space to have a larger size than a size of a second memory space used in data transfer in the second port, the securing unit securing a size of the first memory space and a size of the second memory space based on a ratio of duration of the first time period and duration of the second time period; and a dividing unit that divides each of the first memory space and the second memory space into a reception buffer space, a transmission buffer space, and a retransmission buffer space, the retransmission buffer space storing a packet to be retransmitted responsive to receiving a negative acknowledgment (NAK).

2. The data transfer apparatus according to claim 1 , further comprising: a first measuring unit that measures the first time period, and a second measuring unit that measures the second time period, wherein based on the first time period measured by the first measuring unit and the second time period measured by the second measuring unit.

3. The data transfer apparatus according to claim 1 , further comprising: a calculating unit that calculates the second time period based on length of a cable connected to the second port, and when the first time period is longer than the second time period calculated by the calculating unit, the securing unit secures the size of the first memory space to be larger than the size of the second memory space.

4. The data transfer apparatus according to claim 1 , wherein each of the first port and the second port is a port compliant to peripheral component interconnect (PCI) express standard, and the first time period and the second time period are based on transmission of a transaction layer packet (TLP) up to reception of an acknowledgement (ACK) or the negative acknowledgment (NAK) as a response to transmitted TLP in the first port and the second port, respectively.

5. The data transfer apparatus according to claim 1 , wherein the securing unit secures sizes of each of the reception buffer space, the transmission buffer space, and the retransmission buffer space in the first memory space that are used for data transfer in the first port to have a larger size than sizes of each of the reception buffer space, the transmission buffer space, and the retransmission buffer space in the second memory space that are used for data transfer in the second port.

6. The data transfer apparatus according to claim 1 , wherein a respective first portion of each of the reception buffer space, the transmission buffer space, and the retransmission buffer space in the first memory is divided from the first memory space, and a respective second portion of each of the reception buffer space, the transmission buffer space, and the retransmission buffer space in the second memory is divided from the second memory space such that each of the respective first portions is larger in size than each of the respective second portions.

7. A data transfer device comprising: a first port and a second port that communicate data; a memory unit that stores the data; a securing unit that secures, when a first time period starting from transmission of data up to reception of a response to transmitted data at the first port is longer than a second time period starting from transmission of data up to reception of a response to transmitted data at the second port, a first memory space that is used in data transfer in the first port so as for the first memory space to have a larger size than a size of a second memory space used in data transfer in the second port, the securing unit securing a size of the first memory space and a size of the second memory space based on a ratio of duration of the first time period and duration of the second time period; and a dividing unit that divides each of the first memory space and the second memory space into a reception buffer space, a transmission buffer space, and a retransmission buffer space, the retransmission buffer space storing a packet to be retransmitted responsive to receiving a negative acknowledgment (NAK).

8. The data transfer device according to claim 7 , wherein a respective first portion of each of the reception buffer space, the transmission buffer space, and the retransmission buffer space in the first memory is divided from the first memory space, and a respective second portion of each of the reception buffer space, the transmission buffer space, and the retransmission buffer space in the second memory is divided from the second memory space such that each of the respective first portions is larger in size than each of the respective second portions.

9. A data transfer method in a data transfer device that includes a first port, a second port, a securing unit, and a dividing unit, the method comprising: transmitting data by the first port; transmitting data by the second port; securing, by the securing unit, when a first time period starting from transmission of data up to reception of a response to transmitted data at the first port is longer than a second time period starting from transmission of data up to reception of a response to transmitted data at the second port, a first memory space that is used in data transfer in the first port so as for the first memory size to have a larger size than a size of a second memory space used in data transfer in the second port, the securing unit securing a size of the first memory space and a size of the second memory space based on a ratio of duration of the first time period and duration of the second time period; and dividing, by the dividing unit, each of the first memory space and the second memory space into a reception buffer space, a transmission buffer space, and a retransmission buffer space, the retransmission buffer space storing a packet to be retransmitted responsive to receiving a negative acknowledgment (NAK).

10. The data transfer method according to claim 9 , wherein a respective first portion of each of the reception buffer space, the transmission buffer space, and the retransmission buffer space in the first memory is divided from the first memory space, and a respective second portion of each of the reception buffer space, the transmission buffer space, and the retransmission buffer space in the second memory is divided from the second memory space such that each of the respective first portions is larger in size than each of the respective second portions.